Demands for developing environment-friendly energy are increasing. Power generation using a wind turbine is spotlighted globally.
For the installation of a wind turbine, environmental conditions and installation conditions should be considered. For example, as the environmental conditions, an installation site of the wind turbine, for the realization of effective rotation by blades, requires wind speed faster than a preset wind speed and a very wide area.
Moreover, as the installation conditions, the installation site of the wind turbine should be free from noise caused by the drive of the wind turbine.
Recently, for the relative freedom from the above environmental conditions or the restrictions, concerns to the wind turbines are increasing.
A marine wind turbine may be installed by various ways, but can be generally installed such that parts are manufactured into several units on the land, and that the manufactured units are transported on the sea for assembly.
For example, a wind turbine installation vessel (WTIV) is to transport the marine wind turbine unit manufactured on the land to the installation site and to install the same at the installation site on the sea.
The WTIV may be used in a transit mode and a jack-up mode in view of operating properties.
Specifically, the WTIV sails to a site where the marine turbine is installed in the transit mode. In the transit mode, legs may be elevated up to the upper side of a main body for the purpose of decreasing resistance caused by sea water. After that, the operating mode of the WTIV is switched to the jack-up mode such that the legs are lowered down and are driven into the seabed and the main body is elevated along the legs such that the main body may be spaced apart from the surface of the sea by a preset distance. When the main body reaches a preset position, the WTIV stops to move the main body and carries out the installation of the marine wind turbine, and moves to a next installation site by performing the above installation order reversely after the installation.
In the floating structure, as a leg support or a jack case supporting and driving the legs projects upward from a hull of the floating structure or a main deck of the main body, the space availability of the main deck may be relatively deteriorated in loading loads by functions of the floating structure.
For example, in a case when the floating structure is a ship or a marine structure for installing the marine wind turbine, a shipping space for the load such as a plurality of blades, a nacelle, a tower, and the like corresponding to parts of the marine wind turbine may be restricted due to the leg support projecting upward from the main deck.
Moreover, when to dispose the jack case in the floating structure simply, it is difficult to install the jack case in an internal structural material of the floating structure and it is required to solve sealing of the jacking unit, installation of a plurality of jacking units including motors and pinions in the jack case and maintenance thereof.